1. Field of the Invention
The present invention relates to an electromagnetic switch capable of turning on and turning off an electric contact mounted on an energized electric circuit of a starter motor.
2. Description of the Related Art
In order to satisfy recent demand of reducing the fuel consumption for saving energy in vehicles, an automatic engine-stop system is adopted to many vehicles. For example, when a driver stops his vehicle at an intersection when the stop lamp (red or yellow lamp) of a traffic signal is lighting, the automatic engine-stop system mounted on the vehicle controls so that the vehicle is automatically fallen into the idling stop condition. As a result, the engine of the vehicle halts temporary for saving the fuel consumption. A silent engine start of the vehicle is very necessary for the driver when the engine of the vehicle restarts when the green or blue lamp of the traffic signal.
For example, Japanese patent laid open publication No. H5-126018 as a conventional technique has disclosed an electromagnetic switch mounted on a starter which is capable of starting an engine mounted on the vehicle. In the electromagnetic switch, a current flow through a magnetic coil enables to magnetize a stationary iron core, and thereby to form an electromagnet. The magnetic force of the electromagnet attracts and holds a plunger as a movable iron core. The electromagnetic attraction to the plunger closes a main contact of an energized electric circuit mounted on a starter motor for the engine of the vehicle.
However, a conventional electromagnetic switch causes a large impact noise or a large crashing sound when the plunger is attracted to and collides with the stationary iron core by the energized electromagnet. This impact noise becomes an obstacle to perform the silent engine start. In particular, because a vehicle capable of performing the idling stop frequently restarts, it is necessary to reduce operation noise of the electromagnetic switch in order to achieve the silent engine start, where the operation noise of the electromagnetic switch is an impact noise generated when the plunger is attracted to and collides with the stationary iron core.